MP6540H Basic Operation

[chisatholm]

I’m really struggling with the bring up of a new PCB incorporating the MP6540H. I would very much like to get the MP device working (so I don’t have to go back to the ancient-but-works DRV8313).

I’m trying to drive a 3 phase BLDC motor using PWM. I’ve incorporated the MP6540H and an MCU on a test PCB.

I connected nSLEEP to the MCU, which is running at 3V3. The MP6540H is running at 10V.

ENA, ENB & ENC are joined together and wired to a GPIO of the same MCU. In what follows I’ll call this one connection ENABC.

PWMA, B & C are driven at 3V3 by the MCU using centre aligned PWM mode. These inputs look good on the scope, and they’ve been set up as a slowly moving sin(wt), sin(wt + 120), sin(wt + 240) pattern.

With SLEEPn and ENABC both high, SA, SB and SC are essentially just some noise - see image 1.

With ENABC low (contrary to the datasheet) and no load I see 10V appear at the MP6540H output pins and then decay - see image 2.

With ENABC low and an inductive load (GM5208-12 motor) I see a curvy output voltage - see image 3. There is no current to speak of - my bench supply says it’s supplying 11mA, but the MCU is probably taking a good chunk of that.

I’m really at a loss to understand the behaviour. The normal multimeter poking and prodding suggests that the chip is correctly soldered to the PCB without shorts. I include a portion of my schematic in case it reveals the problem.

Any help would be much appreciated!

[chisatholm]

It seems I ordered the MP6540HA instead of the MP6540H, which would explain the weird behaviour. If anybody from MPS is monitoring this, please take a look and see if you agree with me that it is easy to make this mistake.

Right at the top of the datasheet, it says:
MP6540H, MP6540HA.

Now, call me old-fashioned, but that rather strongly implies to me that the names of the parts are:
MP6540H, MP6540HA.

But actually, if you order an MP6540HGU-A-Z you get an MP6540HA. I you want an MP6540H, you better order an MP6540HGU-P.

It is many years since I ordered the wrong part on an electronics project. Nobody else puts critical part number info after the dash. Do they?? Show me! Why not write MP6540HGU and MP6540HGU-A at the top of the datasheet? Then everyone knows where they need to look to spot the difference.

I invite MPS to consider whether the user journey could be improved. If MPS would like to refund me the ~$100 I wasted on a pointless PCB, that would go a long way to making me feel less grumpy about the itinerant “A”.

Grumpily yours etc, ….